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<TITLE>Performance of the Electron and Photon Trigger in p-p Collisions at sqrt(s) = 900 GeV</TITLE>
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<H1 ALIGN=CENTER><I>Performance of the Electron and Photon Trigger in p-p Collisions at sqrt(s) = 900 GeV</I></H1>
<P ALIGN=CENTER><B>ATLAS-CONF-2010-022</B></P><P ALIGN=CENTER>20 April 2010</P><TABLE WIDTH=800 ALIGN=CENTER CELLPADDING=5 CELLSPACING=1 BGCOLOR=#002000 FRAME=box>
<TR bgcolor=#ffffe0><TH>Content</TH><TH>Preview</TH></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><A HREF="ATLAS-CONF-2010-022.pdf">Main document (PDF, 393kB)</A>
</TD><TD ALIGN=CENTER>-</TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 1</I>:<BR>Fraction of events in which the L1 EM3 trigger found at least one cluster above 3 trigger counts within the data selected by the minimum bias scintillators (MBTS) as a function of the run number. 
 This fraction is given with respect to the number of events 
 selected by the minimum bias trigger. Only runs which 
 contained more than 20000 collision candidates were taken into account.
<BR><A HREF="fig_01.eps">eps, 10kB</A><BR><A HREF="fig_01.png">png, 19kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_01.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 2</I>:<BR>L1 EM trigger rate as a function of the threshold for cosmic and 
 collision candidates. Overall rates are shown for all events passing the EM3 
 trigger as well as for 
 collision candidates for which the timing difference in the
 two sides of the minimum scintillators is required to be within 10~ns
 (MBTS req). In addition, the event rate passing the
 requirement for muons from cosmic ray events (cosmic req) are shown 
 These muons are selected by EM3 but not the MBTS trigger.
 Furthermore, the rate for one run taken during cosmic ray data taking is 
 given. This is evidence that the events failing the 
 MBTS selection arise predominantly from cosmic muons.  
 The rates are normalised to correspond to one pair of colliding bunches.
<BR><A HREF="fig_02.eps">eps, 12kB</A><BR><A HREF="fig_02.png">png, 43kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_02.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 3</I>:<BR>L1 efficiency for the trigger selecting electromagnetic clusters
 above 3 counts (~3 GeV) as a function of the raw offline cluster 
 transverse energy. The turn-on is shown for data (black triangles) and MC 
 simulation (red points).
<BR><A HREF="fig_03.eps">eps, 11kB</A><BR><A HREF="fig_03.png">png, 36kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_03.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 4a</I>:<BR>Comparison of the distributions of the shower shape R_eta
 calculated at L2 for data and simulation.
<BR><A HREF="fig_04a.eps">eps, 13kB</A><BR><A HREF="fig_04a.png">png, 28kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_04a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 4b</I>:<BR>Comparison of the distributions of the shower shape R_eta
 calculated at EF for data and simulation.
<BR><A HREF="fig_04b.eps">eps, 13kB</A><BR><A HREF="fig_04b.png">png, 27kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_04b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 5a</I>:<BR>Comparison of the distributions of the energy found in the
 strip with maximal energy deposit in the first EM layer
 found at L2 for data and simulation.
<BR><A HREF="fig_05a.eps">eps, 14kB</A><BR><A HREF="fig_05a.png">png, 30kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_05a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 5b</I>:<BR>Comparison of the distributions of the energy found in the
 strip with maximal energy deposit in the first EM layer
 found at EF for data and simulation.
<BR><A HREF="fig_05b.eps">eps, 14kB</A><BR><A HREF="fig_05b.png">png, 31kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_05b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 6</I>:<BR>Distribution of F_side calculated at the EF level for data and simulation.
<BR><A HREF="fig_06.eps">eps, 13kB</A><BR><A HREF="fig_06.png">png, 29kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_06.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 7a</I>:<BR>Distribution of the shower shape variable R_eta found at L2 versus the same quantity calculated at the EF level. 
<BR><A HREF="fig_07a.eps">eps, 11kB</A><BR><A HREF="fig_07a.png">png, 26kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_07a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 7b</I>:<BR>Difference in R_eta between the values found by
 the trigger and the offline reconstruction.
<BR><A HREF="fig_07b.eps">eps, 12kB</A><BR><A HREF="fig_07b.png">png, 25kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_07b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 8a</I>:<BR>Difference between the energy of the strips with maximal energy in the first EM layer E_1^max found by L2 and EF respectively
 and the offline.
<BR><A HREF="fig_08a.eps">eps, 11kB</A><BR><A HREF="fig_08a.png">png, 25kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_08a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 8b</I>:<BR>Difference between F_side reconstructed by the EF and the offline.
<BR><A HREF="fig_08b.eps">eps, 9kB</A><BR><A HREF="fig_08b.png">png, 23kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_08b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 9</I>:<BR>Example of an electron candidate passing the medium offline 
 selections as seen by the L2 algorithms. The particle deposits 
 its energy in the first and second EM layer and the reconstructed
 IdScan track points straight at the cluster. In addition on the right side, the transverse energy of the L1 trigger towers are shown.
<BR><A HREF="fig_09.eps">eps, 1501kB</A><BR><A HREF="fig_09.png">png, 291kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_09.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 10a</I>:<BR>Comparison of the eta difference between
 the track extrapolated into the first EM layer and the barycentre
 of the cell energies in this layer
 calculated at L2 for data and simulation. The
 contribution of electrons from conversions is shown separately.
<BR><A HREF="fig_10a.eps">eps, 10kB</A><BR><A HREF="fig_10a.png">png, 28kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_10a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 10b</I>:<BR>Comparison of the eta difference between
 the track extrapolated into the first EM layer and the barycentre
 of the cell energies in this layer
 calculated at EF for data and simulation. The
 contribution of electrons from conversions is shown separately.
<BR><A HREF="fig_10b.eps">eps, 9kB</A><BR><A HREF="fig_10b.png">png, 27kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_10b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 11a</I>:<BR>Comparison of the E/p distributions
 calculated at L2 for data and simulation. The
 contribution of electrons from conversions is shown separately.
<BR><A HREF="fig_11a.eps">eps, 11kB</A><BR><A HREF="fig_11a.png">png, 27kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_11a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 11b</I>:<BR>Comparison of the E/p distributions
 calculated at EF for data and simulation. The
 contribution of electrons from conversions is shown separately.
<BR><A HREF="fig_11b.eps">eps, 12kB</A><BR><A HREF="fig_11b.png">png, 30kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_11b.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 12a</I>:<BR>Difference between the cluster and track eta positions found by the HLT and 
 the offline. The distributions are shown for L2 and EF separately.
<BR><A HREF="fig_12a.eps">eps, 9kB</A><BR><A HREF="fig_12a.png">png, 23kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_12a.png"></TR>
<TR bgcolor=fefefe><TD ALIGN=CENTER><I>Figure 12b</I>:<BR>E/p distribution found by the HLT and the offline. The distributions are shown
 for L2 and EF separately.
<BR><A HREF="fig_12b.eps">eps, 9kB</A><BR><A HREF="fig_12b.png">png, 24kB</A><BR>
</TD><TD ALIGN=CENTER><IMG SRC=".thumb_fig_12b.png"></TR>
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